Experimental and numerical study of group effect on the behavior of helical piles in soft clays under uplift and lateral loading

Abstract

The applications of helical piles have grown significantly and they have become more popular for construction, especially as a potential offshore foundation system in recent years, owing to their distinct benefits over alternative systems. Helical piles may be installed in groups to support heavy loads; therefore, a reliable design requires an accurate assessment of their behavior. The present study used finite element modeling to extensively analyze the uplift and lateral behavior of group piles installed in soft clay soil. The problem was modeled using Plaxis 3D software, and the model was validated using laboratory scale model test data. The validated model is then utilized to investigate the group effect for three distinct configurations, namely rectangular, triangular, and square patterns, with helical piles placed at varied center-to-center spacing's. The term “group efficiency” is used to describe the group effect of each group on the ultimate capacity. The findings showed that the group efficiency is significantly influenced by the number of piles, center-to-center pile spacing, and the failure criteria assumed to interpret test data. The load-transfer mechanism was also investigated and reported for varying group configurations. Finally, for the assumed failure criteria, the provision of an optimum spacing ratio is suggested for both tensile and laterally loaded group helical piles.